This invention relates to multiwell apparatus for biological and biochemical analyses.
Microwell test plates, inclusive of the so-called microtiter test plates, have been adapted for a wide range of biological and biochemical laboratory procedures. Most of such apparatus currently in use has been standardized to enable use in conjunction with a standard 96 well microtiter plate having a 12 by 8 array of microwells.
Multiwell trays characterized as "microfiltration trays" are disclosed by U.S. Pat. No. 3,319,792 issued to Leder et al, U.S. Pat. No. 3,730,352 issued to Cohen et al, U.S. Pat. No. 3,888,770 issued to Avital et al, U.S. Pat. No. 3,963,615 issued to Plakas, U.S. Pat. No. 4,167,875 issued to Meakin, U.S. Pat. No. 4,317,726 issued to Shepel, U.S. Pat. No. 4,427,415 issued to Cleveland, U.S. Pat. No. 4,526,690 issued to Kiovsky et al and UK 1,490,362. Similar plates, specifically intended for cell culture are disclosed by U.S. Pat. No. 4,304,865 issued to O'Brien et al, U.S. Pat. No. 4,483,925 issued to Noack and PCT publication W086/07606. Seiler-et al - U.S. Pat. No. 4,079,009 and Kremer - U.S. Pat. No. 3,928,203 disclose similar microwell plates adapted for use in microchromatography. Likewise, numerous different designs for microwell plates intended for use in immunodiffusion techniques have been patented, e.g. Saravis - U.S. Pat. No. 3,378,347 and Goldsmith - U.S. Pat. No. 3,390,962. U.S. Pat. No. 4,090,850 issued to Chen et al and U.S. Pat. No. 4,246,339 issued to Cole et al disclose multiwell plates specifically designed for immunoassays. All such apparatus disclosed by the prior art includes at least one plate member having an array of wells closed at the bottom with a porous or microporous filter member or membrane. The terminology "microfiltration apparatus" and "multiwell filtration plate" as used herein is intended to embrace all such types of apparatus, regardless of the nature of the permeable medium at the bottom of the individual test wells.
Only a few of the prior art designs for microfiltration apparatus provide for separate collection of the filtrate emanating from the individual wells. With most of the prior art apparatus, attempts to separately collect the filtrate from each well would be unsuccessful or suffer from unreliable results due to cross-contamination between the wells by wicking, capillary action, spilling, running, etc. Further, with many of the prior art designs the apparatus must be used with a separate capital vacuum manifold which is expensive and represents a considerable investment. This is particularly limiting in applications such as genetic research where it is desirable to use numerous microfiltration plates simultaneously. Also, the use of a separate capital manifold limits the ability to stack more than one microfiltration plate in applications requiring serial passage of fluid through more than one plate. An additional problem with much of the prior art microwell apparatus is that little or no provision is made for sanitary handling of the residual materials at the completion of the test. This is a particularly acute problem in assays of bodily fluids containing potentially contagious viral strains and in the case of radiography test procedures where it becomes necessary to handle residual materials and apparatus contaminated by radioactivity.